Newly-proposed anode-free zinc-ion batteries(ZIBs)are promising to remarkably enhance the energy density of ZIBs,but are restricted by the unfavorable zinc deposition interface that causes poor cycling stability.Herei...Newly-proposed anode-free zinc-ion batteries(ZIBs)are promising to remarkably enhance the energy density of ZIBs,but are restricted by the unfavorable zinc deposition interface that causes poor cycling stability.Herein,we report a Cu-Zn alloy network-modulated zinc deposition interface to achieve stable anode-free ZIBs.The alloy network can not only stabilize the zinc deposition interface by suppressing 2D diffusion and corrosion reactions but also enhance zinc plating/stripping kinetics by accelerating zinc desolvation and nucleation processes.Consequently,the alloy network-modulated zinc deposition interface realizes high coulombic efficiency of 99.2%and high stability.As proof,Zn//Zn symmetric cells with the alloy network-modulated zinc deposition interface present long operation lifetimes of 1900 h at 1 m A/cm^(2)and 1200 h at 5 m A/cm^(2),significantly superior to Zn//Zn symmetric cells with unmodified zinc deposition interface(whose operation lifetime is shorter than 50 h),and meanwhile,Zn3V3O8cathodebased ZIBs with the alloy network-modified zinc anodes show notably enhanced rate capability and cycling performance than ZIBs with bare zinc anodes.As expected,the alloy network-modulated zinc deposition interface enables anode-free ZIBs with Zn3V3O8cathodes to deliver superior cycling stability,better than most currently-reported anode-free ZIBs.This work provides new thinking in constructing high-performance anode-free ZIBs and promotes the development of ZIBs.展开更多
Magnesium alloys are lightweight materials with great potential,and plasma electrolytic oxidation(PEO)is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys.However,the∼1...Magnesium alloys are lightweight materials with great potential,and plasma electrolytic oxidation(PEO)is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys.However,the∼14µm thick and rough PEO protection layer has inferior wear resistance,which limits magnesium alloys as sliding or reciprocating parts,where magnesium alloys have special advantages by their inherent damping and denoising properties and attractive light-weighting.Here a novel super wear-resistant coating for magnesium alloys was achieved,via the discontinuous sealing(DCS)of a 1.3µm thick polytetrafluoroethylene(PTFE)polymer layer with an initial area fraction(A_(f))of 70%on the necessary PEO protection layer by selective spraying,and the wear resistance was exceptionally enhanced by∼5500 times in comparison with the base PEO coating.The initial surface roughness(Sa)under PEO+DCS(1.54µm)was imperfectly 59%higher than that under PEO and conventional continuous sealing(CS).Interestingly,DCS was surprisingly 20 times superior for enhancing wear resistance in contrast to CS.DCS induced nano-cracks that splitted DCS layer into multilayer nano-blocks,and DCS also provided extra space for the movement of nano-blocks,which resulted in rolling friction and nano lubrication.Further,DCS promoted mixed wear of the PTFE polymer layer and the PEO coating,and the PTFE layer(HV:6 Kg·mm^(−2),A_(f):92.2%)and the PEO coating(HV:310 Kg·mm^(−2),A_(f):7.8%)served as the soft matrix and the hard point,respectively.Moreover,the dynamic decrease of Sa by 29%during wear also contributed to the super wear resistance.The strategy of depositing a low-frictional discontinuous layer on a rough and hard layer or matrix also opens a window for achieving super wear-resistant coatings in other materials.展开更多
Electrochemical behaviors of Zn-Fe alloy and Zn-Fe-TiO2 composite electrodeposition in alkaline zincatesolutions were studied respectively by the methods of linear potential sweep and cyclic voltammetry. From the re-s...Electrochemical behaviors of Zn-Fe alloy and Zn-Fe-TiO2 composite electrodeposition in alkaline zincatesolutions were studied respectively by the methods of linear potential sweep and cyclic voltammetry. From the re-sults it can be concluded that Zn shows under potential deposition, Zn-Fe alloy codeposition is anomalous codeposi-tion and Zn-Fe alloy cathode polarization is increased with the introduction of additive. From the view point of elec-trochemistry, the reasons that the content of Fe in the Zn-Fe coating changes with the composition of the electrolyteand the process conditions altering and the relationship between the content of Fe and the appearance of the coatingare interpreted. The cathode polarization of Zn-Fe alloy codeposition is enhanced obviously with addition of additive.In the course of composite electrodeposition, TiO2 has less promotion to electrodeposition of zinc ions than to iron i-ons, while the electrodeposition of iron ions improves the content of TiO2 in composite coating, which is inagreement with the results of process experiments.展开更多
In recent years,wire-arc directed energy deposition(wa DED),which is also commonly known as wire-arc additive manufacturing(WAAM),has emerged as a promising new fabrication technique for magnesium alloys.The major rea...In recent years,wire-arc directed energy deposition(wa DED),which is also commonly known as wire-arc additive manufacturing(WAAM),has emerged as a promising new fabrication technique for magnesium alloys.The major reason for this is the possibility of producing parts with a complex geometry as well as a fine-grained microstructure.While the process has been shown to be applicable for Mg-Al-Zn alloys,there is still a lack of knowledge in terms of the influence of the WAAM process on the age-hardening response.Consequently,this study deals with the aging response of a WAAM AZ91 alloy.In order to fully understand the mechanisms during aging,first,the as-built condition was analyzed by means of high-energy X-ray diffraction(HEXRD)and scanning electron microscopy.These investigations revealed a finegrained,equiaxed microstructure with adjacent areas of alternating Al content.Subsequently,the difference between single-and double-step aging as well as conventional and direct aging was studied on the as-built WAAM AZ91 alloy for the first time.The aging response during the various heat treatments was monitored via in situ HEXRD experiments.Corroborating electron microscopy and hardness studies were conducted.The results showed that the application of a double-step aging heat treatment at 325℃with pre-aging at 250℃slightly improves the mechanical properties when compared to the single-step heat treatment at 325℃.However,the hardness decreases considerably after the pre-aging step.Thus,aging at lower temperatures is preferable within the investigated temperature range of 250-325℃.Moreover,no significant difference between the conventionally aged and directly aged samples was found.Lastly,the specimens showed enhanced precipitation kinetics during aging as compared to cast samples.This could be attributed to a higher amount of nucleation sites and the particular temperature profile of the solution heat treatment.展开更多
Additive friction stir deposition(AFSD)is a novel structural repair and manufacturing technology has become a research hotspot at home and abroad in the past five years.In this work,the microstructural evolution and m...Additive friction stir deposition(AFSD)is a novel structural repair and manufacturing technology has become a research hotspot at home and abroad in the past five years.In this work,the microstructural evolution and mechanical performance of the Al-Mg-Si alloy plate repaired by the preheating-assisted AFSD process were investigated.To evaluate the tool rotation speed and substrate preheating for repair quality,the AFSD technique was used to additively repair 5 mm depth blind holes on 6061 aluminum alloy substrates.The results showed that preheat-assisted AFSD repair significantly improved joint bonding and joint strength compared to the control non-preheat substrate condition.Moreover,increasing rotation speed was also beneficial to improve the metallurgical bonding of the interface and avoid volume defects.Under preheating conditions,the UTS and elongation were positively correlated with rotation speed.Under the process parameters of preheated substrate and tool rotation speed of 1000 r/min,defect-free specimens could be obtained accompanied by tensile fracture occurring in the substrate rather than the repaired zone.The UTS and elongation reached the maximum values of 164.2MPa and 13.4%,which are equivalent to 99.4%and 140%of the heated substrate,respectively.展开更多
This paper presents the results of a study concerned with the surface hardening of Fe-based alloys and WC-8Co cemented carbide by inte- grating laser cladding and the electrospark deposition processes. Specimens of lo...This paper presents the results of a study concerned with the surface hardening of Fe-based alloys and WC-8Co cemented carbide by inte- grating laser cladding and the electrospark deposition processes. Specimens of low carbon steel were processed firstly by laser cladding with Fe-based alloy powders and then by electrospark deposition with WC-SCo cemented carbide. It is shown that, for these two treatments, the electrospark coating possesses finer microstructure than the laser coating, and the thickness and surface hardness of the electrospark coating can be substantially increased.展开更多
A new technique of electroplating amorphous Fe-Ni-W alloy deposits was proposed.The structure and morphology o Fe-Ni-W alloy deposit were detected by XRD and SEM.The friction and wear behavior of Fe-Ni-W alloy deposit...A new technique of electroplating amorphous Fe-Ni-W alloy deposits was proposed.The structure and morphology o Fe-Ni-W alloy deposit were detected by XRD and SEM.The friction and wear behavior of Fe-Ni-W alloy deposit were studied and compared with that of chromium deposit.The corrosion properties against 5% sodium chloride,5% sulfuric acid and 5% sodium hydroxide were also discussed.The experimental results indicate that Fe-Ni-W alloy deposits have superior properties against wea than hard chromium deposits under dry sliding condition.Under oil sliding condition,except their better wear resistance,the deposits can protect their counterparts against wear.The deposits plated on brass and AISI 1045 steel show good behavior against corrosion o 5% sodium chloride,5% sulfuric acid and 5% sodium hydroxide.The bath of electroplating amorphous Fe-Ni-W alloy deposits is environmentally friendly and would find widely use in industry.展开更多
Al-10.8Zn-2.8Mg-1.9Cu alloy was synthesized by spray atomization and deposition technique. GP zones and age-hardening process in the alloy were investigated using high-resolution electron microscopy (HREM), selected...Al-10.8Zn-2.8Mg-1.9Cu alloy was synthesized by spray atomization and deposition technique. GP zones and age-hardening process in the alloy were investigated using high-resolution electron microscopy (HREM), selected area diffraction (SAD), and differential scanning calorimetry (DSC) analysis. The results indicated that spray deposition process accelerated the aging kinetics of the alloy at an aging temperature of 120℃, thereby reducing the peak aging time to 16 h. GPⅠ and GPⅡ are the two types of zones that are major precipitates for the alloy under peak-aged condition. The precipitation sequence for the alloy is also discussed.展开更多
High strength Al-Zn-Mg-Cu alloys were prepared by spray deposition and casting techniques. The microstructures of the Al-Zn-Mg-Cu alloys were studied using scanning electron microscopy, transmission electron microscop...High strength Al-Zn-Mg-Cu alloys were prepared by spray deposition and casting techniques. The microstructures of the Al-Zn-Mg-Cu alloys were studied using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Secondary phases in the microstructures of the alloys prepared by spray deposition and conventional cast were examined. The results indicate that under the conventional casting condition, the microstructure of the alloy revealed the presence of coarse Al/Mg(ZnCu)2 eutectic phases, and the spray deposited process causes an obvious modification in size, morphology, and distribution of secondary phases in the microstructure as well as reduction of segregation. The superior microstructure of the spray-deposited Al-Zn-Mg-Cu alloy was attributed to the high cooling rate, and associated with the rapid solidification process.展开更多
A heat resistant aluminum alloy pipe blank with dimensions of d 700/300 mm×1 200 mm was prepared by the multi layer spray deposition technology. Optical microscopy, X ray diffractometry and transmission electron ...A heat resistant aluminum alloy pipe blank with dimensions of d 700/300 mm×1 200 mm was prepared by the multi layer spray deposition technology. Optical microscopy, X ray diffractometry and transmission electron microscopy were used to analyze its morphologies and microstructures. The results show that the microstructures of the pipe blank are homogeneous and the precipitates are uniformly distributed d 25~70 nm spherical or sphere like Al 12 (Fe,V) 3Si particles, its mechanical properties at room temperature and 350 ℃ after densification by extrusion are σ b=412 MPa, δ =7.6% and σ b=187 MPa, δ =7.6%, respectively. The analyses indicate that the proper match of the motion rates of atomizer and substrate can produce deposited blanks with uniform thickness and relatively high cooling rate.展开更多
This article examines fatigue crack nucleation and propagation in laser deposited TC18 titanium alloy. The Widmanstatten structure was obtained by double-annealing treatment,. High-cycle fatigue (HCF) tests were con...This article examines fatigue crack nucleation and propagation in laser deposited TC18 titanium alloy. The Widmanstatten structure was obtained by double-annealing treatment,. High-cycle fatigue (HCF) tests were conducted at room temperature with the stress ratio of 0.1 and the notch concentration factor Kt = 1. Fatigue cracks initiated preferentially at micropores, which had great effect on the HCF properties. The effect decreased with the decrease of pore size and the increase of distance from the pore location to the specimen surface. The crack initiation region was characterized by the cleavage facets of a lamella and the tearing of β matrix. The soft a precipitated-free zone formed along grain boundaries accelerated the crack propagation. Subsurface observation indicated that the crack preferred to propagate along the grain boundary α or border of a lamella or vertical to a lamella.展开更多
The cylindrical billets of a Mg-3Al-1Zn (AZ31) alloy were synthesized by spray deposition processing. The microstructure evolution and mechanical properties of the alloy were investigated. The results reveal that th...The cylindrical billets of a Mg-3Al-1Zn (AZ31) alloy were synthesized by spray deposition processing. The microstructure evolution and mechanical properties of the alloy were investigated. The results reveal that the microstructure of the AZ31 alloy is refined significantly by spray deposition processing. A homogeneous and equiaxial-grain structure with an average grain size of 17 μm is obtained. Further grain refinement with an average grain size of 5 μm is attributed to dynamic recrystallization during extrusion processing. The great increase in the density of grain boundary nucleation sites by the finer initial grain sizes makes the dislocation pile-ups near subgrain boundaries being absorbed easily by the boundaries, resulting in an accelerated recrystallization process. The average tensile ultimate and yield strengths of the extruded rods are 321 MPa and 237 MPa, respectively, with an elongation of 15.2% at room temperature, which are remarkably higher than those of the conventional as-cast AZ31 alloy.展开更多
Ni-W alloys and their composite deposits are electroplated on the metals when an appropriate complex agent is selected on the base of the theories of electrochemistry and complex chemistry, and the principle of induce...Ni-W alloys and their composite deposits are electroplated on the metals when an appropriate complex agent is selected on the base of the theories of electrochemistry and complex chemistry, and the principle of induced codeposition. Effects of the bath composition, pH value, temperature and current density on the electrode position of Ni-W alloys and their composite deposits have been investigated, and the effect of heat treatment temperature on the hardness, structure and cohesive force of the amorphous Ni-W alloys and their composite deposits are also discussed. Results showed that the alloys containing more than 44 wt pct W content and the composite deposits containing 7.8 wt pct SiC content could be obtained by making use of the appropriate bath composition and plating conditions. Alloys and their composite deposits with over 44 wt pct W content show amorphous structure. The hardness of amorphous Ni-W alloys and their composite deposits increases obviously when heated, and can reach to 1350 HV and 1520 HV respectively for 46 wt pct W content. The cohesion on Cu, carbon steel and stainless steel is very good.展开更多
Laser direct deposition (LDD) of metallic components is an advanced technology of combining CAD/CAM (computer aided design/computer aided manufacturing), high power laser, and rapid prototyping. This technology us...Laser direct deposition (LDD) of metallic components is an advanced technology of combining CAD/CAM (computer aided design/computer aided manufacturing), high power laser, and rapid prototyping. This technology uses laser beam to melt the powders fed coaxiaUy into the molten pool by the laser beam to fabricate fuUy dense metallic components. The present article mainly studies the LDD of Ti-6Al-4V alloy, which can be used to fabricate aircraft components. The mechanical properties of the Ti-6Al-4V alloy, fabricated by LDD, are obtained using the tension test, and the oxygen content of used powders and deposited specimens are measured. In the present article, it can be seen that the mechanical properties obtained using this method are higher than the ones obtained by casting, and equal to those got by wrought anneal. One aircraft part has been made using the LDD process. Because of this aircraft part, with sophisticated shape, the effect of the laser scanning track on the internal soundness of the deposited part was discussed.展开更多
A technology for electroless Ni-P deposition on AZ91D from a low cost plating bath containing sulfate nickel was proposed. The seal pretreatment was employed before the electroless Ni-P deposition for the sake of occl...A technology for electroless Ni-P deposition on AZ91D from a low cost plating bath containing sulfate nickel was proposed. The seal pretreatment was employed before the electroless Ni-P deposition for the sake of occluding the micro holes of the cast magnesium alloy and interdicting the bubble formation in the Ni-P coating during plating process. And pickling pretreatment can provide a better adhesion between the Ni-P deposition and AZ91D substrate. The deposition speed of the Ni-P coating is 29 μm/h. The technology is employed to AZ91D magnesium alloy automobile parts and can provide high hardness and high wear-resistant. The weight losses of Ni-P plated and heat-treated Ni-P plated magnesium alloy specimen are only about 1/6 and 1/10 that of bare magnesium alloy specimen after 10 min abrasion wear, respectively. The hardness of the electroless Ni-P plated brake pedal support brackets is 674.1 VHN and 935.7 VHN after 2 hours heat treatments at 180 C. The adhesion of Ni-P coatings on magnesium alloy substrates meets the demands of ISO Standards 2819. The technology is environment friendly and cannot cause hazard to environment because of absence of chromate in the whole process.展开更多
Two thixoforming technologies of 6066 aluminum alloy (Al 1.37Si 1.37Mg 0.77Cu 0.07Mn ) produced by multi layer spray deposition process were studied. The spray formed materials are of equiaxed and very fine grain (10...Two thixoforming technologies of 6066 aluminum alloy (Al 1.37Si 1.37Mg 0.77Cu 0.07Mn ) produced by multi layer spray deposition process were studied. The spray formed materials are of equiaxed and very fine grain (10~20 μm). And the grain size coarsens slower than that of conventional casting materials at temperature below the liquidus, which may relate to high temperature particles distributed along the grain boundaries. Extrusion and hot pressing were used as the thixoforming processes respectively. After extrusion the materials show a microstructure of mean grain size below 20 μm without obvious recrystallization. The mechanical properties achieved via extrusion and pressing in semi solid state attain that of common wrought materials with shorter peak aging time of 4~5 h, about half of that in conventional condition. [展开更多
The preparation, formation mechanism, surface appearance and structure of electroless plating Fe-Mo-W-B amorphous alloys were systematically studied. The deposition rates of the deposits in different bath composition ...The preparation, formation mechanism, surface appearance and structure of electroless plating Fe-Mo-W-B amorphous alloys were systematically studied. The deposition rates of the deposits in different bath composition as plated were measured. The formation mechanism of the deposits was discussed. The parameter for amorphous structures formation was suggested for the deposits.展开更多
基金financial support provided by the National Natural Science Foundation of China(52002149)the Guangdong Basic and Applied Basic Research Foundation(2020A1515111202)+1 种基金the Special Funds for the Cultivation of Guangdong College Students’Scientific and Technological Innovation(“Climbing Program”Special Funds)(pdjh2022a0056)the Fundamental Research Funds for the Central Universities。
文摘Newly-proposed anode-free zinc-ion batteries(ZIBs)are promising to remarkably enhance the energy density of ZIBs,but are restricted by the unfavorable zinc deposition interface that causes poor cycling stability.Herein,we report a Cu-Zn alloy network-modulated zinc deposition interface to achieve stable anode-free ZIBs.The alloy network can not only stabilize the zinc deposition interface by suppressing 2D diffusion and corrosion reactions but also enhance zinc plating/stripping kinetics by accelerating zinc desolvation and nucleation processes.Consequently,the alloy network-modulated zinc deposition interface realizes high coulombic efficiency of 99.2%and high stability.As proof,Zn//Zn symmetric cells with the alloy network-modulated zinc deposition interface present long operation lifetimes of 1900 h at 1 m A/cm^(2)and 1200 h at 5 m A/cm^(2),significantly superior to Zn//Zn symmetric cells with unmodified zinc deposition interface(whose operation lifetime is shorter than 50 h),and meanwhile,Zn3V3O8cathodebased ZIBs with the alloy network-modified zinc anodes show notably enhanced rate capability and cycling performance than ZIBs with bare zinc anodes.As expected,the alloy network-modulated zinc deposition interface enables anode-free ZIBs with Zn3V3O8cathodes to deliver superior cycling stability,better than most currently-reported anode-free ZIBs.This work provides new thinking in constructing high-performance anode-free ZIBs and promotes the development of ZIBs.
基金This work was financially supported by the Jiangsu Distinguished Professor Project,the Innovate UK(Project reference:10004694)the National Key R&D Program of China 2021YFB3401200.The Experimental Techniques Centre at Brunel University London and Nanjing University of Aeronautics and Astronautics are acknowledged.The authors also acknowledge the characterization facility at Shanghai Jiao Tong University,Central South University,University of Birmingham and University of Lille.
文摘Magnesium alloys are lightweight materials with great potential,and plasma electrolytic oxidation(PEO)is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys.However,the∼14µm thick and rough PEO protection layer has inferior wear resistance,which limits magnesium alloys as sliding or reciprocating parts,where magnesium alloys have special advantages by their inherent damping and denoising properties and attractive light-weighting.Here a novel super wear-resistant coating for magnesium alloys was achieved,via the discontinuous sealing(DCS)of a 1.3µm thick polytetrafluoroethylene(PTFE)polymer layer with an initial area fraction(A_(f))of 70%on the necessary PEO protection layer by selective spraying,and the wear resistance was exceptionally enhanced by∼5500 times in comparison with the base PEO coating.The initial surface roughness(Sa)under PEO+DCS(1.54µm)was imperfectly 59%higher than that under PEO and conventional continuous sealing(CS).Interestingly,DCS was surprisingly 20 times superior for enhancing wear resistance in contrast to CS.DCS induced nano-cracks that splitted DCS layer into multilayer nano-blocks,and DCS also provided extra space for the movement of nano-blocks,which resulted in rolling friction and nano lubrication.Further,DCS promoted mixed wear of the PTFE polymer layer and the PEO coating,and the PTFE layer(HV:6 Kg·mm^(−2),A_(f):92.2%)and the PEO coating(HV:310 Kg·mm^(−2),A_(f):7.8%)served as the soft matrix and the hard point,respectively.Moreover,the dynamic decrease of Sa by 29%during wear also contributed to the super wear resistance.The strategy of depositing a low-frictional discontinuous layer on a rough and hard layer or matrix also opens a window for achieving super wear-resistant coatings in other materials.
文摘Electrochemical behaviors of Zn-Fe alloy and Zn-Fe-TiO2 composite electrodeposition in alkaline zincatesolutions were studied respectively by the methods of linear potential sweep and cyclic voltammetry. From the re-sults it can be concluded that Zn shows under potential deposition, Zn-Fe alloy codeposition is anomalous codeposi-tion and Zn-Fe alloy cathode polarization is increased with the introduction of additive. From the view point of elec-trochemistry, the reasons that the content of Fe in the Zn-Fe coating changes with the composition of the electrolyteand the process conditions altering and the relationship between the content of Fe and the appearance of the coatingare interpreted. The cathode polarization of Zn-Fe alloy codeposition is enhanced obviously with addition of additive.In the course of composite electrodeposition, TiO2 has less promotion to electrodeposition of zinc ions than to iron i-ons, while the electrodeposition of iron ions improves the content of TiO2 in composite coating, which is inagreement with the results of process experiments.
基金supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020the financial support of the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Grant No.771146 TOUGHIT)funded within the AIT’s strategic research portfolio 2022 and by the European Commission within the framework INTERREG V-A Austria–Czech Republic in the project“ReMaP“(Interreg project no.ATCZ229)。
文摘In recent years,wire-arc directed energy deposition(wa DED),which is also commonly known as wire-arc additive manufacturing(WAAM),has emerged as a promising new fabrication technique for magnesium alloys.The major reason for this is the possibility of producing parts with a complex geometry as well as a fine-grained microstructure.While the process has been shown to be applicable for Mg-Al-Zn alloys,there is still a lack of knowledge in terms of the influence of the WAAM process on the age-hardening response.Consequently,this study deals with the aging response of a WAAM AZ91 alloy.In order to fully understand the mechanisms during aging,first,the as-built condition was analyzed by means of high-energy X-ray diffraction(HEXRD)and scanning electron microscopy.These investigations revealed a finegrained,equiaxed microstructure with adjacent areas of alternating Al content.Subsequently,the difference between single-and double-step aging as well as conventional and direct aging was studied on the as-built WAAM AZ91 alloy for the first time.The aging response during the various heat treatments was monitored via in situ HEXRD experiments.Corroborating electron microscopy and hardness studies were conducted.The results showed that the application of a double-step aging heat treatment at 325℃with pre-aging at 250℃slightly improves the mechanical properties when compared to the single-step heat treatment at 325℃.However,the hardness decreases considerably after the pre-aging step.Thus,aging at lower temperatures is preferable within the investigated temperature range of 250-325℃.Moreover,no significant difference between the conventionally aged and directly aged samples was found.Lastly,the specimens showed enhanced precipitation kinetics during aging as compared to cast samples.This could be attributed to a higher amount of nucleation sites and the particular temperature profile of the solution heat treatment.
基金financially supported by Science and Technology Major Project of Changsha,China(No.kh2401034)the Fundamental Research Funds for the Central Universities of Central South University(No.CX20230182)the National Key Research and Development Project of China(No.2019YFA0709002)。
文摘Additive friction stir deposition(AFSD)is a novel structural repair and manufacturing technology has become a research hotspot at home and abroad in the past five years.In this work,the microstructural evolution and mechanical performance of the Al-Mg-Si alloy plate repaired by the preheating-assisted AFSD process were investigated.To evaluate the tool rotation speed and substrate preheating for repair quality,the AFSD technique was used to additively repair 5 mm depth blind holes on 6061 aluminum alloy substrates.The results showed that preheat-assisted AFSD repair significantly improved joint bonding and joint strength compared to the control non-preheat substrate condition.Moreover,increasing rotation speed was also beneficial to improve the metallurgical bonding of the interface and avoid volume defects.Under preheating conditions,the UTS and elongation were positively correlated with rotation speed.Under the process parameters of preheated substrate and tool rotation speed of 1000 r/min,defect-free specimens could be obtained accompanied by tensile fracture occurring in the substrate rather than the repaired zone.The UTS and elongation reached the maximum values of 164.2MPa and 13.4%,which are equivalent to 99.4%and 140%of the heated substrate,respectively.
文摘This paper presents the results of a study concerned with the surface hardening of Fe-based alloys and WC-8Co cemented carbide by inte- grating laser cladding and the electrospark deposition processes. Specimens of low carbon steel were processed firstly by laser cladding with Fe-based alloy powders and then by electrospark deposition with WC-SCo cemented carbide. It is shown that, for these two treatments, the electrospark coating possesses finer microstructure than the laser coating, and the thickness and surface hardness of the electrospark coating can be substantially increased.
基金Project(04GK1007) supported by the Science and Technology Office of Hunan Province,China
文摘A new technique of electroplating amorphous Fe-Ni-W alloy deposits was proposed.The structure and morphology o Fe-Ni-W alloy deposit were detected by XRD and SEM.The friction and wear behavior of Fe-Ni-W alloy deposit were studied and compared with that of chromium deposit.The corrosion properties against 5% sodium chloride,5% sulfuric acid and 5% sodium hydroxide were also discussed.The experimental results indicate that Fe-Ni-W alloy deposits have superior properties against wea than hard chromium deposits under dry sliding condition.Under oil sliding condition,except their better wear resistance,the deposits can protect their counterparts against wear.The deposits plated on brass and AISI 1045 steel show good behavior against corrosion o 5% sodium chloride,5% sulfuric acid and 5% sodium hydroxide.The bath of electroplating amorphous Fe-Ni-W alloy deposits is environmentally friendly and would find widely use in industry.
基金This work was financially supported by the Major State Basic Research Development Program of China (No. 2005CB623704).
文摘Al-10.8Zn-2.8Mg-1.9Cu alloy was synthesized by spray atomization and deposition technique. GP zones and age-hardening process in the alloy were investigated using high-resolution electron microscopy (HREM), selected area diffraction (SAD), and differential scanning calorimetry (DSC) analysis. The results indicated that spray deposition process accelerated the aging kinetics of the alloy at an aging temperature of 120℃, thereby reducing the peak aging time to 16 h. GPⅠ and GPⅡ are the two types of zones that are major precipitates for the alloy under peak-aged condition. The precipitation sequence for the alloy is also discussed.
基金This work was financially supported by the Major State Basic Besearch Development Program of China (No.2005CB623704)The authors wish to thank professors Shao B.L.and Liu A.S.(National Analysis and Testing Center for Nonferrous Metals & Electronic Materials,General Research Institute for Nonferrous Metals) for the TEM work,and Li Y.L.(Analysis and Test Center,Beijing Normal University) for SEM work.
文摘High strength Al-Zn-Mg-Cu alloys were prepared by spray deposition and casting techniques. The microstructures of the Al-Zn-Mg-Cu alloys were studied using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Secondary phases in the microstructures of the alloys prepared by spray deposition and conventional cast were examined. The results indicate that under the conventional casting condition, the microstructure of the alloy revealed the presence of coarse Al/Mg(ZnCu)2 eutectic phases, and the spray deposited process causes an obvious modification in size, morphology, and distribution of secondary phases in the microstructure as well as reduction of segregation. The superior microstructure of the spray-deposited Al-Zn-Mg-Cu alloy was attributed to the high cooling rate, and associated with the rapid solidification process.
文摘A heat resistant aluminum alloy pipe blank with dimensions of d 700/300 mm×1 200 mm was prepared by the multi layer spray deposition technology. Optical microscopy, X ray diffractometry and transmission electron microscopy were used to analyze its morphologies and microstructures. The results show that the microstructures of the pipe blank are homogeneous and the precipitates are uniformly distributed d 25~70 nm spherical or sphere like Al 12 (Fe,V) 3Si particles, its mechanical properties at room temperature and 350 ℃ after densification by extrusion are σ b=412 MPa, δ =7.6% and σ b=187 MPa, δ =7.6%, respectively. The analyses indicate that the proper match of the motion rates of atomizer and substrate can produce deposited blanks with uniform thickness and relatively high cooling rate.
基金financially supported by the Cheung Kong Scholars Innovative Research Team Program of Ministry of Education, China (No. IRT0805)the State Key Basic Research Program of China (No. 2011CB606305)
文摘This article examines fatigue crack nucleation and propagation in laser deposited TC18 titanium alloy. The Widmanstatten structure was obtained by double-annealing treatment,. High-cycle fatigue (HCF) tests were conducted at room temperature with the stress ratio of 0.1 and the notch concentration factor Kt = 1. Fatigue cracks initiated preferentially at micropores, which had great effect on the HCF properties. The effect decreased with the decrease of pore size and the increase of distance from the pore location to the specimen surface. The crack initiation region was characterized by the cleavage facets of a lamella and the tearing of β matrix. The soft a precipitated-free zone formed along grain boundaries accelerated the crack propagation. Subsurface observation indicated that the crack preferred to propagate along the grain boundary α or border of a lamella or vertical to a lamella.
基金supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project, the Ministry of Education of China
文摘The cylindrical billets of a Mg-3Al-1Zn (AZ31) alloy were synthesized by spray deposition processing. The microstructure evolution and mechanical properties of the alloy were investigated. The results reveal that the microstructure of the AZ31 alloy is refined significantly by spray deposition processing. A homogeneous and equiaxial-grain structure with an average grain size of 17 μm is obtained. Further grain refinement with an average grain size of 5 μm is attributed to dynamic recrystallization during extrusion processing. The great increase in the density of grain boundary nucleation sites by the finer initial grain sizes makes the dislocation pile-ups near subgrain boundaries being absorbed easily by the boundaries, resulting in an accelerated recrystallization process. The average tensile ultimate and yield strengths of the extruded rods are 321 MPa and 237 MPa, respectively, with an elongation of 15.2% at room temperature, which are remarkably higher than those of the conventional as-cast AZ31 alloy.
文摘Ni-W alloys and their composite deposits are electroplated on the metals when an appropriate complex agent is selected on the base of the theories of electrochemistry and complex chemistry, and the principle of induced codeposition. Effects of the bath composition, pH value, temperature and current density on the electrode position of Ni-W alloys and their composite deposits have been investigated, and the effect of heat treatment temperature on the hardness, structure and cohesive force of the amorphous Ni-W alloys and their composite deposits are also discussed. Results showed that the alloys containing more than 44 wt pct W content and the composite deposits containing 7.8 wt pct SiC content could be obtained by making use of the appropriate bath composition and plating conditions. Alloys and their composite deposits with over 44 wt pct W content show amorphous structure. The hardness of amorphous Ni-W alloys and their composite deposits increases obviously when heated, and can reach to 1350 HV and 1520 HV respectively for 46 wt pct W content. The cohesion on Cu, carbon steel and stainless steel is very good.
基金This work was supported by the National Natural Science Foundation of China (No. 50331010)
文摘Laser direct deposition (LDD) of metallic components is an advanced technology of combining CAD/CAM (computer aided design/computer aided manufacturing), high power laser, and rapid prototyping. This technology uses laser beam to melt the powders fed coaxiaUy into the molten pool by the laser beam to fabricate fuUy dense metallic components. The present article mainly studies the LDD of Ti-6Al-4V alloy, which can be used to fabricate aircraft components. The mechanical properties of the Ti-6Al-4V alloy, fabricated by LDD, are obtained using the tension test, and the oxygen content of used powders and deposited specimens are measured. In the present article, it can be seen that the mechanical properties obtained using this method are higher than the ones obtained by casting, and equal to those got by wrought anneal. One aircraft part has been made using the LDD process. Because of this aircraft part, with sophisticated shape, the effect of the laser scanning track on the internal soundness of the deposited part was discussed.
基金Foundation of National Key Basic Research and Development Program(No.2004CB619301)Project 985-Automotive Engineering of Jilin University
文摘A technology for electroless Ni-P deposition on AZ91D from a low cost plating bath containing sulfate nickel was proposed. The seal pretreatment was employed before the electroless Ni-P deposition for the sake of occluding the micro holes of the cast magnesium alloy and interdicting the bubble formation in the Ni-P coating during plating process. And pickling pretreatment can provide a better adhesion between the Ni-P deposition and AZ91D substrate. The deposition speed of the Ni-P coating is 29 μm/h. The technology is employed to AZ91D magnesium alloy automobile parts and can provide high hardness and high wear-resistant. The weight losses of Ni-P plated and heat-treated Ni-P plated magnesium alloy specimen are only about 1/6 and 1/10 that of bare magnesium alloy specimen after 10 min abrasion wear, respectively. The hardness of the electroless Ni-P plated brake pedal support brackets is 674.1 VHN and 935.7 VHN after 2 hours heat treatments at 180 C. The adhesion of Ni-P coatings on magnesium alloy substrates meets the demands of ISO Standards 2819. The technology is environment friendly and cannot cause hazard to environment because of absence of chromate in the whole process.
文摘Two thixoforming technologies of 6066 aluminum alloy (Al 1.37Si 1.37Mg 0.77Cu 0.07Mn ) produced by multi layer spray deposition process were studied. The spray formed materials are of equiaxed and very fine grain (10~20 μm). And the grain size coarsens slower than that of conventional casting materials at temperature below the liquidus, which may relate to high temperature particles distributed along the grain boundaries. Extrusion and hot pressing were used as the thixoforming processes respectively. After extrusion the materials show a microstructure of mean grain size below 20 μm without obvious recrystallization. The mechanical properties achieved via extrusion and pressing in semi solid state attain that of common wrought materials with shorter peak aging time of 4~5 h, about half of that in conventional condition. [
文摘The preparation, formation mechanism, surface appearance and structure of electroless plating Fe-Mo-W-B amorphous alloys were systematically studied. The deposition rates of the deposits in different bath composition as plated were measured. The formation mechanism of the deposits was discussed. The parameter for amorphous structures formation was suggested for the deposits.